A common requirement in current advanced semiconductor processing is for underfill material to be placed around connector terminals that provide physical and electrical connection between an integrated circuit die and a substrate. Ball grid array (“BGA”) and flip-chip integrated circuit packages typically include one or more integrated circuit dies mounted to a surface of a substrate. The substrate may further be overmolded to further protect the integrated circuit devices. In a BGA example, the substrate then has, on an opposite surface or in an area designated for it, external ball grid array connectors that provide electrical connectivity to a system board.
In flip chip packaging, after flip chip integrated circuits are mounted on the substrate, an underfill material is provided. The underfill may be provided by a capillary dispensing method, where liquid underfill material flows beneath the dies by capillary action. After the underfill is dispensed and cured, an overmolding process may then be performed and this process provides a mold compound package for the flip chip integrated circuits. This approach requires several steps and is time consuming. The underfill provides a stress relief buffer and protects the connectors and the integrated circuit dies from mechanical stress such as may be caused by thermal cycling.
Recently molded underfill (“MUF”) has been used. In MUF processing, the need for a separate overmolding process is eliminated. The MUF material provides both the underfill beneath the integrated circuit dies and surrounding the connectors, and a protective overmolded package. However the known approaches to forming molded underfills in flip chip mounted integrated circuits have several problems. Voids are commonly formed in the MUF material, warpage of the MUF and the substrate are observed, and the known processes for MUF lack good process control and uniformity in the finished devices, resulting in low yields.
The drawings, schematics and diagrams are illustrative and not intended to be limiting, but are examples of embodiments of the disclosure, are simplified for explanatory purposes, and are not drawn to scale.